New cement bags allow 20 % less bag weight - LS technology saves on material not on performance
BSW Machinery, the Vienna based subsidiary of Windmöller & Hölscher, presented a fascinating new technology for woven PP bags in its show room near Vienna. The technology combines several developments which together allow the reduction of bag weight without losing any of the performance criteria. Key elements are advanced ex-trusion technology for higher tape tenacity and indexed micro perforation. Reduced weight leads to lower bag cost and improved sustainability.
Various sectors of industry use paper and woven PP bags as proven packaging solution. In both areas Windmöller & Hölscher along with BSW Machinery are leading the technology development for many years, especially in extrusion and conversion machinery. Both of these strengths were combined to achieve a significant technology jump. The new Light & Strong technology (LS) will allow bag producers to greatly reduce their material usage. Critical areas of the bags are made stronger compared to older technologies, the overall thickness and weight of the bag material can be reduced while maintaining current strength.
For cement bags 80 grams per bag are quite common. BSW produced bags with 64 grams, filled with cement and performed drop-tests with the result that LS bags easily excel conven-tional bags.
Higher tape strength increases profitability
Tape strength directly influences the weight of a woven PP bag. It shall meet certain me-chanical bag requirements like impact resistance at bag drop. For a wide range of bags an increase of strength can directly be transferred into a lighter bag. As the raw material domi-nates up to 80% of the cost of a bag, every increase in strength can reduce the production cost for a converter. Also, less material directly results in less energy per bag needed in ex-trusion.
Up to now higher strength values were compromising the elasticity or vice versa. Now, the new processing technology implemented on BSW’s tape extrusion line tiraTex has broken down this old barrier. Even with standard PP grades which are commonly used in the industry, tenacity values of up to 7 g/den can be achieved with elongation at break values ranging between 25% and 30%. The processing characteristics are designed by the experts at BSW to provide the best results even at highest outputs and production speeds of 500 m/min or more.
Higher edge strength increases profitability
Micro- or nano perforation provides the needed holes for bag ventilation during the filing pro-cess. However, each hole is weakening the tapes which define the strength of the bag. Especially the feather edges are vulnerable when handling or dropping the bags. The new LS concept protects crucial edges and other areas through indexed perforation. The perforation is disengaged whenever crucial sections of bag material are passing through the bag con-version machine. Synchronization ensures that the unperforated areas are matching to the print on the bag and are placed such that in the final bag the critical zones are built from un-perforated material.
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